The particular router with which the present invention finds utility includes a motor housing having an external cylindrical portion, with a cutting tool mounted at one end of the motor housing to the shaft of the motor supported within the motor housing. The cylindrical portion has a first longitudinal region with a substantially smooth surface and a second longitudinal region with an external screw thread. The router also includes a base having a cylindrical bore for slidably receiving therein the first longitudinal region of the motor housing cylindrical portion. The depth of cut adjustment mechanism includes an adjustment ring which is split with an opening between two opposed ends The adjustment ring engages the screw thread on the motor housing and rotationally engages the base, whereby rotation of the adjustment ring effects relative longitudinal motion between the motor housing and the base so that the distance which the cutting tool projects beyond the base may be varied It is an object of this invention to provide an arrangement for releasably securing the adjustment ring to the motor housing and the base so as to maintain the position of the base relative the motor housing.
Prior router depth of cut adjustment mechanisms utilizing a split adjustment ring have included projections on opposite sides of the split which are squeezed together to effect a clamping action by means of a threaded member arranged generally tangential to the ring. These arrangements are not entirely satisfactory because, for example, there is insufficient room for manipulating the threaded member. Such arrangements are usually of two general configurations. First is an arresting screw having a knob as shown in U.S. Pat. Nos. 4,566,830 and 3,443,479. Such a configuration enables equal amounts of force being applied to the knob for purposes of tightening and loosening of the arresting screw in order to select a predetermined depth of the cutting tool.
An alternative form of threaded members is in the shape of a wing-nut as disclosed in U.S. Pat. Nos. 4,319,860; 4,316,685; 4,239,428; and 2,613,704. The wing-nut configuration enables an equal amount of force to be applied in both the fastening direction and the loosening direction for purposes of moving the adjustment ring relative to the motor housing to select a predetermined depth of cut.
Vibration of the drive unit in the router results in further tightening of the threaded member. The combination of large amounts of force being applied to the threaded member by hand tightening in conjunction with the vibration of the motor results in the necessity of excess torque being required to loosen the threaded member.
U.S. Pat. Nos. 131,843; 3,313,198; and 1,929,116 disclose one-way screws capable of being securely fastened but which results in slippage of a screw driver or the like when the screws are attempted to be removed because of a helical ramp surface in a direction opposite that of the fastening direction. Such configurations, however, do not provide finger grips for hand-tightening nor do they provide a means for exerting additional force upon the screw for loosening same.
A threaded member for use with a router capable of limiting the amount of hand-tightening in one direction while providing a means for exerting a greater force in an opposite direction for loosening of the threaded member has not been taught or suggested in existing patents. It is therefore another object of this invention to provide a more effective split ring clamping arrangement.